Add 3042_count_prefix_and_suffix_pairs_one

m3xw3ll · m3xw3ll · commit aece34c888a3 · 2025-04-10T12:03:58.000+02:00
diff --git a/Algorithms/3042_count_prefix_and_suffix_pairs.one.md b/Algorithms/3042_count_prefix_and_suffix_pairs.one.md
@@ -0,0 +1,49 @@
+# [Count Prefix and Suffix Pairs I](https://leetcode.com/problems/count-prefix-and-suffix-pairs-i/description/)
+
+You are given a 0-indexed string array words.
+
+Let's define a boolean function isPrefixAndSuffix that takes two strings, str1 and str2:
+
+isPrefixAndSuffix(str1, str2) returns true if str1 is both a prefix and a suffix of str2, and false otherwise.
+For example, isPrefixAndSuffix("aba", "ababa") is true because "aba" is a prefix of "ababa" and also a suffix, but isPrefixAndSuffix("abc", "abcd") is false.
+
+Return an integer denoting the number of index pairs (i, j) such that i < j, and isPrefixAndSuffix(words[i], words[j]) is true.
+
+Example 1:
+```
+Input: words = ["a","aba","ababa","aa"]
+Output: 4
+Explanation: In this example, the counted index pairs are:
+i = 0 and j = 1 because isPrefixAndSuffix("a", "aba") is true.
+i = 0 and j = 2 because isPrefixAndSuffix("a", "ababa") is true.
+i = 0 and j = 3 because isPrefixAndSuffix("a", "aa") is true.
+i = 1 and j = 2 because isPrefixAndSuffix("aba", "ababa") is true.
+Therefore, the answer is 4.
+```
+Example 2:
+```
+Input: words = ["pa","papa","ma","mama"]
+Output: 2
+Explanation: In this example, the counted index pairs are:
+i = 0 and j = 1 because isPrefixAndSuffix("pa", "papa") is true.
+i = 2 and j = 3 because isPrefixAndSuffix("ma", "mama") is true.
+Therefore, the answer is 2.  
+```
+Example 3:
+```
+Input: words = ["abab","ab"]
+Output: 0
+Explanation: In this example, the only valid index pair is i = 0 and j = 1, and isPrefixAndSuffix("abab", "ab") is false.
+Therefore, the answer is 0.
+```
+Solution
+```python
+class Solution:
+    def countPrefixSuffixPairs(self, words: List[str]) -> int:
+        cnt = 0
+        for a in range(len(words)):
+            for b in range(a + 1, len(words)):
+                if words[b].startswith(words[a]) and words[b].endswith(words[a]):
+                    cnt += 1
+        return cnt
+```
diff --git a/Algorithms/snippets/3042_count_prefix_and_suffix_pairs_one.py b/Algorithms/snippets/3042_count_prefix_and_suffix_pairs_one.py
@@ -0,0 +1,10 @@
+def count_prefix_suffix_pairs(words):
+    cnt = 0
+    for a in range(len(words)):
+        for b in range(a + 1, len(words)):
+            if words[b].startswith(words[a]) and words[b].endswith(words[a]):
+                cnt += 1
+    return cnt
+
+
+print(count_prefix_suffix_pairs(words = ["a","aba","ababa","aa"]))
diff --git a/README.md b/README.md
@@ -755,6 +755,7 @@ To search for a specific problem please use ```STRG + F``` to search for.
 | 3000   | [Maximum Area of Longest Diagonal Rectangle](https://github.com/m3xw3ll/LeetCode/blob/master/Algorithms/3000_maximum_area_of_longest_diagonal_rectangle.md)      
 | 3005   | [Count Elements With Maximum Frequency](https://github.com/m3xw3ll/LeetCode/blob/master/Algorithms/3005_count_elements_with_maximum_frequency.md)
 | 3019   | [Number of Changing Keys](https://github.com/m3xw3ll/LeetCode/blob/master/Algorithms/3019_number_of_changing_keys.md)
+| 3042   | [Count Prefix and Suffix Pairs I](https://github.com/m3xw3ll/LeetCode/blob/master/Algorithms/3042_count_prefix_and_suffix_pairs_one.md)
 | 3065   | [Minimum Operations to Exceed Threshold Value I](https://github.com/m3xw3ll/LeetCode/blob/master/Algorithms/3065_minimum_operations_to_exceed_threshold_value_one.md)
 | 3069   | [Distribute Elements Into Two Arrays I](https://github.com/m3xw3ll/LeetCode/blob/master/Algorithms/3069_distribute_elements_into_two_arrays_one.md)
 | 3074   | [Apple Redistribution into Boxes](https://github.com/m3xw3ll/LeetCode/blob/master/Algorithms/3074_apple_redistribution_into_boxes.md)
